Various methods have been used to adjust light beam throw length, beam size, and intensity for spotlights. Theaters generally are of such a size that the beam is focused between the approximate throw ranges of around 100 feet and 200 feet.
The light projector generally used in the art of theater spotlights is an ellipsoidal type that reflects the light from the lamp to a focal area spaced from the lamp from where the light spreads outwardly in a cone. An iris receives and passes the cone of light to focusing lenses.
Recent advances in the art of ellipsoidal reflector lamp assemblies has created candlepowers far beyond those delivered by prior art assemblies, except for high intensity carbon or Xenon arc lights. This new development has also created the opportunity to modify the spotlight to change candlepower ranges. In particular, the new General Electric Mark 350 reflector lamp assembly now being marketed can deliver up to about 12 million candle power on about 300 watts of power as compared to the old systems that deliver for example, about 2.4 million candle power from a 575 watt lamp or 10 million candle power from 1200 watts. The new GE lamp is a small lamp that can create a high intensity from very low wattage. This in turn creates opportunities for new spotlight adjustment systems relating to beam range and illumination that would formerly have been of marginal value.
Adjustment of the reflector lamp assembly relative to the iris is known. For example, U.S. Pat. No. 4,338,654 teaches the movement of the reflector relative to the iris and a simultaneous automatic opening and closing of the diaphragm iris by way of the same controls with the reflector so that the aperture of the iris diaphragm always captures the full beam being emmanated from the focal area of the light reflected from the reflector.
While the inventiveness of the above-described prior art patent is not to be minimized, it is nevertheless worth mentioning a serious drawback of the mechanism. That is, the iris diaphragm is not adjustable relative to the movement of the reflector. The lack of flexibility seriously flaws the usefulness of the mechanism. As one example of this lack of flexibility is the case where a certain intensity of illumination is required to stage in a wide spot and then a small spot is required. If the reflector assembly and iris diaphragm are linked, then the wide spot will have a low intensity and the small spot will have a high intensity with a possible variation exceeding a ten to one ratio. Such intensity changes are unacceptable when compared to other stage illumination, especially if TV or film cameras are being used due to the contrast of limits of the cameras.
Another disadvantage of prior art systems is that a spotlight is made either for a long throw beam, about 200 feet to stage, or a short throw beam, around 100 feet to stage. In former spotlight systems this inflexible construction was standard which requires a multiplicity of spotlight assemblies to meet all requirements.
Accordingly, it is an object of the present invention to provide a spotlight system that is flexible in its applicability over a wide range of theatrical situations that call for varied light intensity, range, and beam spread.
It is another object of this invention to provide a spotlight system which incorporates a reflector-lamp assembly of high intensity and low wattage whose beam of light is adjustable relative to an iris.
It is yet another object of this invention to provide a spotlight system that provides both an adjustable reflector-lamp assembly and an independently adjustable iris that can be adjusted simultaneously with the movement of the reflector.
It is yet another object of this invention to provide a spotlight system that provides an independently adjustable iris that can be widened or closed as the adjustable reflector-lamp assembly is moved from or towards the iris respectively in order to pass that portion of the illuminative power passed from the reflector that is required on stage.
It is still a further object of this invention to provide a spotlight system that includes a pair of spaced mountings each of which is adapted to receive a fixed front lens so that a single spotlight housing can be adapted as a short throw or a long throw spotlight system.
In accordance with these and other objects, there is provided a spotlight adjusting system for controlling the beam of a spotlight that comprises a base structure, an elliposidal reflector-lamp assembly mounted on the structure adapted to reflect light rays to a focal area; an iris mounted on the structure spaced from the reflector-lamp assembly for selectively controlling the passage of light rays from the focal area; a fixed front lens mounted on the structure; and a rear focusing lens mounted on the structure used to focus the light rays from the iris into a light beam directed by the front lens to an area remote from the spotlight. The reflector-lamp assembly is movable to a plurality of positions between a forward position and a rearward position, the forward position being nearer to the iris than the rearward position. The diaphragm of the iris is independently adjustable relative to the reflector-lamp assembly so that the light rays being radiated from the focal area can be gathered in their entirety and passed to the lenses, or the light rays can be reduced to a selected luminosity and sent to the lenses.